Muting circuit for AM stereophonic receiver
US4383136A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 17, 1981 |
| Grant date | May 10, 1983 |
| Priority date | — |
| Expiry date | Jun 17, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G3/341
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A muting circuit for an AM stereophonic receiver of the type in which a received signal is phase modulated with a sub signal and amplitude modulated with a main signal and in which noise generated under certain adverse conditions is eliminated. A first detection signal is generated when the level of a received AM stereophonic signal is lower than a predetermined value, a second detection signal is generated upon detection of a non-locked state of a phase-locked loop circuit used to detect the sub signal, a third detection signal is generated when a frequency deviation detection senses is that a free-running frequency of a voltage controlled oscillator in the phase-locked loop circuit and a frequency of the AM stereophonic signal are different in frequency by more than a predetermined value; and a fourth detection signal is generated when a stereo pilot signal is absent. A muting circuit is activated in response to any of first through fourth detection signals. The frequency deviation detector is preferably implemented as a window detector which has an input-output characteristic including hysteresis.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.